<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
  </head>
  <body>
    <script>
    const arr =[15,19,21,33,18,24]
    let sum = 0
    let average
    for (let i = 0; i<arr.length;i++){
      sum += arr[i]
    }
    document.write(`数组的平均数为${average = sum/arr.length}`)
  </script>
</body>
</html>